1. Field of Invention
This invention relates to cleaning the interproximal spaces between teeth.
2. Prior Art
Dental caries is one of the most common diseases in the world. The gaps between teeth, called interproximal spaces, are some of the most difficult places to clean in order to prevent dental caries. Interproximal spaces can be narrow, especially at the top, making it difficult to insert cleaning devices such as brushes. Thin dental floss and dental tape were created to insert into the narrow top of an interproximal space and clean the space below.
However, floss or tape that is sufficiently thin to insert into the narrow top of the space can be an inefficiently-small tool with which to clean the wider, rounded-wall space below. Often, the floss must be moved back and forth many times in a large number of different angles in order to clean all the rounded surfaces of the wider portion of the interproximal space. Moving the floss back and forth in all of these different angles can be very time consuming and, particularly for teeth toward the back of the mouth, quite cumbersome.
Due to the importance of keeping interproximal spaces clean for prevention of dental caries and the challenges involved with conventional flossing, different approaches to this problem have been pursued in the prior art. However, the ongoing prevalence of dental caries arising from insufficiently-cleaned interproximal spaces is a testimony to the remaining need for better solutions to this problem. The prior art has limitations which are addressed by this current invention. We now discuss the four main approaches to cleaning interproximal spaces in the prior art: interproximal brush; floss with longitudinally-uniform cross-sectional structure; floss with longitudinal variation in cross-sectional structure, and floss with changing cross-sectional structure:
1) Interproximal Brush:
A variety of interproximal brushes are known in the prior art. Brushes have a relatively rigid central core in order to provide sufficient stiffness for insertion into the space and to move the bristles, or other protrusions, back and forth. The bristles or other protrusions generally extend out in a radial and/or perpendicular manner from the central rigid core. The main limitation of interproximal brushes is that a relatively rigid central core is too large to insert into smaller interproximal spaces. Even for larger spaces, a brush may not be able to clean the narrow top portion. Another limitation of brushes is that they are virtually always inserted in one direction, from the outside, and thus do not clean rounded wall surfaces in a symmetric manner. Finally, it can be a challenge to avoid injuring soft mouth tissue with an automated system with a rigid-core brush.
2) Floss with Longitudinally-Uniform Cross-Sectional Structure:
Traditional dental floss has the same general cross-sectional shape throughout its length. Many types of such floss are known in the prior art. Some such floss in the prior art has advanced cross-sectional shapes, textures, abrasiveness, softness, porosity, or elasticity to improve its cleaning ability. For example, see U.S. Pat. Nos. 4,187,390 (Gore), 5,755,243 (Roberts), 5,765,576 (Dolan), 5,830,495 (Ochs), 5,845,652 (Tseng), 6,027,592 (Tseng), 6,039,054 (Park), 6,742,528 (Dave), 7,017,591 (Brown) and 7,025,986 (Brown). However, even advanced longitudinally-uniform floss has limitations. Since the floss must be thin enough to insert through the narrow top of an interproximal space, it often must be moved in a wide range of angles to clean the entire interproximal space, especially when the space is wider at the bottom and teeth on either side are rounded. Moving the floss in such a wide range of angles can be time-consuming and, especially for teeth that are far back in the mouth, can be very cumbersome as well.
3) Floss with Longitudinal Variation in Cross-Sectional Structure:
A variation on traditional dental floss is dental floss with fixed cross-sectional structures at intervals along its length. Such floss can be inserted into the space using a thin section of the floss and then a section of the floss with wider cross-sectional structure can be pulled through the space. Cross-sectional structures can include: cuts or holes as in U.S. Pat. Nos. 4,974,615 (Doundoulakis), 5,293,886 (Czapor), 6,607,000 (Marwah), and 7,055,530 (Husted); longitudinal segments with different diameters or flexibility as in U.S. Pat. Nos. 4,142,538 (Thornton), 4,974,614 (Selker), 5,433,226 (Burch), 5,718,251 (Gray), 7,055,530 (Husted) and 20060225764 (Mark); or protrusions at intervals such as knots, spheres, dimples, bristles, flanges as in U.S. Pat. Nos. 4,836,226 (Wolak), 4,974,615 (Doundoulakis), 5,063,948 (Lloyd), 5,316,028 (Flemming), 5,682,911 (Harada), 5,775,346 (Szyszkowski), 6,003,525 (Katz), 6,112,753 (Arsenault), 6,250,313 (duRees), and 6,672,316 (Weihrauch).
Such floss can reduce the number of angles required to clean an interproximal space compared to longitudinally-uniform floss, but the approach still has limitations. If the cross-sectional protrusions are relatively small and flexible, then a large number of angles is still required to clean a wide space with rounded walls. On the other hand, if the cross-sectional protrusions are relatively large and inflexible, then they may become wedged in the interproximal space or even tear gum tissue. The cross-sectional size of the protruding structures in the prior art can not be adjusted within the interproximal space. The ability to custom adjust cross-sectional size would be desirable to clean interproximal spaces of different sizes.
4) Floss with Changing Cross-Sectional Structure:
For the above reasons, it is desirable to have dental floss or dental tape whose cross-sectional structure can be changed within the interproximal space itself. There has been some, albeit limited, progress toward this goal in the prior art as in U.S. Pat. No. 6,123,982 (Fontana) and (GUM™ Expandable Floss™). The prior art includes dental floss with compressed and/or coated fibers that expand due to friction or chemical reaction (such as exposure to moisture). Floss with this expansion potential is a conceptual advance over traditional floss, but still has limitations. If the floss expands with friction or exposure to moisture, then it may expand prematurely before or during insertion, due to the friction of insertion or moisture on the tops of the teeth.
Also, in the prior art the mass of material in a given cross-sectional slice is not increased, just the volume thereof; thus, it can be difficult to ensure that floss after expansion has sufficient resiliency to thoroughly clean larger spaces. An analogy might help to illustrate this point. Suppose that one has a task that requires moderate abrasive action in a tight space. One might be able to use an unexpanded sponge, coated with a moderately abrasive cleaning powder, for this purpose. However, if one were to expand the volume of the sponge by soaking it in water, then it would be much less resilient for providing the required abrasive action.
The limitations of the prior art may be summarized as follows. Brushes are limited because it is difficult to fit their rigid cores into narrow interproximal spaces or the narrow tops of wider spaces. Traditional floss is limited because of its small diameter relative to the wide, rounded-wall space that it must clean. The many different angles at which traditional floss must be moved to clean the entire space can be time-consuming and, in areas in the back of the mouth, very cumbersome. Floss with fixed cross-sectional structures such as knots, spheres, and bristles are limited because the cross-sectional size of these structures can not be adjusted for different size spaces. Further, protruding cross-sectional structures may become wedged in the interproximal space or even tear gum tissue. Current-generation expandable floss relies on friction or chemical reaction for expansion and may expand prematurely before or during insertion. Also, current-generation expanding floss increases the volume, but not the mass, of material in a given cross-sectional slice. Thus, the expanded floss may not have sufficient resiliency to clean wide spaces. This present invention provides a novel way to clean interproximal spaces that addresses all of these limitations of the prior art.